The United States, which has denied any US role in the killing of an Iranian nuclear scientist and condemned the attack, won Japan's support today for tougher sanctions against Tehran over a nuclear programme that the West fears is for atomic arms.
Japan pledged to take concrete action to cut Iranian oil imports after visiting US treasury secretary Timothy Geithner urged major importer Tokyo to help starve Iran of vital oil revenues. In Iran, sanctions are biting, with the rial currency losing 20 per cent of value against the dollar in the past week.
The Iranian nuclear scientist was blown up in his car by a motorbike hitman, prompting Tehran to blame Israeli and US agents but insist it would not derail a nuclear programme that has raised fears of war and threatened world oil supplies.
Yesterday's morning rush-hour bombing - the fifth daylight attack on technical experts in two years - killed 32-year-old Mostafa Ahmadi-Roshan.
The chemical engineer's driver was also killed, Iranian media said, and a passer-by was slightly hurt.
The killing came in a week of heightened tension: Iran has started an underground uranium enrichment plant and sentenced an American to death for spying; Washington and Europe have stepped up efforts to cripple Iran's oil exports for its refusal to halt work that the West says betrays an ambition to build nuclear weapons. Iran says its aims are entirely peaceful.
Tehran has threatened to choke the West's supply of Gulf oil if its exports are hit by sanctions, drawing a US warning that its navy was ready to open fire to prevent any blockade of the strategic Strait of Hormuz, through which 35 per cent of the world's seaborne traded oil passes.
In Tokyo, Mr Geithner welcomed Tokyo's cooperation in tightening the screws on Tehran, an encouraging sign for Washington after China and Russia rebuffed sanctions on Iranian oil exports.
China, Japan and India are Iran's top three buyers, taking more than 40 per cent of its crude exports. The European Union, a major buyer, has committed to banning imports of oil from Iran, an Opec member and the world's fifth-largest crude exporter.
Japanese prime minister Yoshihiko Noda said he shared serious concerns about Iran's nuclear capabilities but expressed concern that the sanctions could seriously affect the Japanese and world economies depending on how they were implemented.
US president Barack Obama's administration has also announced that it would freeze financial institutions that deal with Iran's central bank out of US markets.
"We are exploring ways to cut Iran's central bank off from the global financial system. We are in the early stages of consulting with Japan and our other allies," Mr Geithner told reporters after the talks with Japanese leaders.
On a visit to Cuba yesterday, Iranian president Mahmoud Ahmadinejad said nothing about the bomb attack but flashed the victory sign and said Iran had done nothing to warrant enmity from its enemies.
"Have we assaulted someone? Have we wanted more than we should have? Never, never. We have only asked to speak about and establish justice," said Mr Ahmadinejad.
Analysts saw the latest assassination, which would have taken no little expertise, as less a reaction to recent events than part of a longer-running, covert effort to thwart Iran's nuclear development programme that has also included suspected computer viruses and mystery explosions.
While fears of war have forced up oil prices, the region has seen periods of sabre-rattling and limited bloodshed before without reaching all-out conflict. But a willingness in Israel, which sees an Iranian atom bomb as a threat to its existence, to attack Iranian nuclear sites, with or without US backing, has heightened the sense that a crisis is coming.
Israel, whose military chief said on Tuesday that Iran could expect to suffer more mysterious mishaps, declined comment on yesterday's bomb attack.
While Israeli or Western involvement seemed plausible to independent analysts, a role for local Iranian factions or other regional interests engaged in a deadly shadow war of bluff and sabotage could not be ruled out.
The Atomic Energy Organisation of Iran, which has failed to persuade the West that its quest for nuclear power has no hidden military goal, said the killing of Ahmadi-Roshan would not deter it: "We will continue our path without any doubt ... Our path is irreversible," it said in a statement carried on television.
"The heinous acts of America and the criminal Zionist regime will not disrupt our glorious path ... The more you kill us, the more our nation will awake."
Iran's leaders, preparing for the first national election since a disputed presidential vote in 2009 brought street protests against 32 years of clerical rule, are struggling to contain internal tensions. Defiance of Israel and Western powers plays well with many who will vote in March.
In Washington, White House spokesman Tommy Vietor said: "The United States had absolutely nothing to do with this ... We strongly condemn all acts of violence, including acts of violence like what is being reported today."
Israel, which has a history of covert killings abroad, declined comment, though army spokesman Yoav Mordechai wrote on Facebook: "I don't know who settled the score with the Iranian scientist, but I am definitely not shedding any tears."
Sabotage - like mysterious reported explosions at military facilities or the Stuxnet computer virus widely suspected to have been deployed by Israel and the United States to disrupt nuclear facilities in 2010 - may have had more direct effects.
However, assassinations may be intended to discourage Iranians with nuclear expertise from working on the programme.
Last month, Iran signalled a willingness to return to a negotiating process which stalled a year ago, though Western officials say a new round of talks is far from certain yet.
Iran's decision to carry out enrichment work deep underground in the once undeclared plant at Fordow, near the holy Shia city of Qom, could make it harder for US or Israeli forces to carry out veiled threats to use force against Iranian nuclear facilities. The move to Fordow could reduce the time available for diplomacy to avert any attack.
Reuters